The present invention relates to a resin-sealed semiconductor device, especially a semiconductor device sealed with a resin covering only one side opposite to the base. More particularly, the present invention relates to a semiconductor device characterized by its sealing resin.
The recent downsizing and miniaturization of electronic machines and equipment is accompanied by semiconductors having reduced size and thickness and improved performance. The conventional semiconductor device is composed of a semiconductor element and a lead frame which are sealed by resin such that both sides thereof are covered except for those parts by which it is mounted on a printed circuit board. Therefore, the miniaturization of semiconductor device itself needs improvement in lead frame (as the base) and sealing resin. As the result, there have been developed TSOP (thin small outline package) and QFP (quad flat package), the former having sealing resin in reduced volume and thickness, the latter having a large number of pins.
In order to reduce the mounting area and to improve the performance, there has been developed a new semiconductor device constructed such that terminals to connect the semiconductor device to the mother board are arranged on the back of the base of the semiconductor device. Unfortunately, this structure has the disadvantage that the semiconductor device is liable to warp because only one side opposite to the base is covered with the sealing resin, unlike the conventional semiconductor device which has both sides thereof covered with the sealing resin. Warping hampers the mounting on a flat mother board, causes peeling at the interface between the base and the semiconductor element, and leads to failure in the thermal cycle test and popcorn resistance test.